Breeding for Resistance to New Races of

Anthracnose Charlie Rodgers

Forage Genetics International

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HISTORY AND RANGE OF ANTHRACNOSE RACES

Race 1 of Anthracnose (Colletotrichum trifolii) is common and widespread.

Race 2 has been reported in a limited geography limited mostly in mid-Atlantic States (1979-1982)

Race 3 in Oklahoma in 1982 – no cultures were maintained Race 4 in Ohio and Australia (2007)

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DISTRIBUTION OF ANTHRACNOSE IN THE U.S.

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EXPECTED RESPONSES OF CHECKS TO RACE1 AND RACE2 ANTHRACNOSE

Race 1 Race 2

Check Expected Expected

Saranac 1 ~0

Saranac AR 45 45

Arc 65-70 ~0

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ANTHRACNOSE SYMPTOMS

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FIELD OBSERVATIONS

In the Spring of 2012 Anthracnose infestations were observed with uncharacteristic timing and severity (2012 Isolate - Samac, et. al., Plant Dis. 98:843, 2014. First Report of Race 2 of Colletotrichum trifolii Causing Anthracnose on Alfalfa in Wisconsin).

In 2014, there was another occurrence of Anthracnose, and diseased stems were harvested and anthracnose was isolated and cultured.

After the 2014 infestation it was decided to initiate a breeding strategy to introduce resistance to these new isolates.

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METHODS STANDARD TESTS - NAAIC

Greenhouse Screen 10” x 20” Flats with Potting Soil (200 seedlings per flat) Spray seedlings at 7-10 days, 1st trifoliate leaf

Inoculum 2012 and 2014 Isolates from FGI - West Salem. 7 day old cultures ½ strength oatmeal agar Conidia concentration 2 x 106 per mL Spray to point of runoff ~ 10 mL Flat

Incubation 2 days ~ 48 hrs at 23C 100 humidity Score 14 days after inoculation

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ANOVA: Split-Plot. Main Plot = Isolate, Subplot = Entry

Factor Type Levels Values Rep random 2 1, 2 Isolate fixed 2 2012, 2014 Entry random 6 414M102, 414M301, 414M311, 414M312, Saranac, Saranac AR Analysis of Variance for %Resis Source DF SS MS F P Rep 1 9.375 9.375 1.33 0.455 Isolate 1 273.375 273.375 16.76 0.034* Isolate(Rep) 1 7.042 7.042 1.13 0.312 Entry 5 202.708 40.542 2.62 0.157 Isolate*Entry 5 77.375 15.475 2.49 0.103 Error 10 62.083 6.208 Total 23 631.958

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Saranac Saranac AR 414M301 414M311 414M312 414M102

% R

esis

tanc

e

Entry

Initial Disease Screens - % Resistance

2012 Isolate 2014 Isolate

2014 FALL ANTHRACNOSE SCREENS

Average % Resistance 2012 = 7.6% 2014 = 1.3%

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BREEDING STRATEGY

Resistant Plants

Adapted Populations

Evaluate And Screen Large Populations

Cross Pollinate

Screen Crosses

Cross Pollinate

Evaluate Crosses

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NEEDLE INOCULATION TO PREVENT ESCAPES SCORED 7 DAYS AFTER INOCULATION

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CROSSING

First round of crossing done in greenhouse. Second round of crossing done under cage.

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2 Cycles of Selection for Anthracnose Resistance have provided tremendous gains.

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Res

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Entry

Fall 2015 Screens - % Resistance 2012 2014

r = 0.58

Average % Resistance 2012 = 43% 2014 = 39%

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% RESISTANCE TO AN1, 2012 AND 2014 ISOLATES

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% R

esist

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Entry

An1

2012 Isolate

2014 Isolate

Average % Resistance An1 = 73% 2012 = 43% 2014 = 39%

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QUESTIONS ?